我应该何时在ActiveMQ中使用JDBC持久性适配器？

Question

Reading the ActiveMQ documentation (we are using the 5.3 release), I find a section about the possibility of using a JDBC persistence adapter with ActiveMQ.

What are the benefits? Does it provide any gain in performance or reliability? When should I use it?

Answer 1

In my opinion, you would use JDBC persistence if you wanted to have a failover broker and you could not use the file system. The JDBC persistence was significantly slower (during our tests) than journaling to the file system. For a single broker, the journaled file system is best.

If you are running two brokers in an active/passive failover, the two brokers must have access to the same journal / data store so that the passive broker can detect and take over if the primary fails. If you are using the journaled file system, then the files must be on a shared network drive of some sort, using NFS, WinShare, iSCSI, etc. This usually requires a higher-end NAS device if you want to eliminate the file share as a single point of failure.

The other option is that you can point both brokers to the database, which most applications already have access to. The tradeoff is usually simplicity at the price of performance, as the journaled JDBC persistence was slower in our tests.

We run ActiveMQ in an active/passive broker pair with journaled persistence via an NFS mount to a dedicated NAS device, and it works very well for us. We are able to process over 600 msgs/sec through our system with no issues.

Answer 2

Hey, the use of journaled JDBC seems to be better than using JDBC persistence only since the journaling is very much faster than JDBC persistence. It is better than just journalled persistence only cos' you have an additional backup of the messages in the db. Journalled JDBC has the additional advantage that the same data in journal is persisted to the db later and this can be accessed by developers when needed!

However, when you are using master/slave ActiveMQ topology with journalled JDBC, you might end up loosing messages since you might have messages in journal that are not yet into the DB!

Answer 3

If you have a redelivery plugin policy in place and use a master/slave setup, the scheduler is used for the redelivery.

As of today, the scheduler can only be setup on a file database, not on the JDBC. If you do not pay attention to that, you will take all messages that are in redelivery out of the HA scenario and local to the broker.

https://issues.apache.org/jira/browse/AMQ-5238 is an issue in Apache issue tracker that asks for a JDBC persistence adapter for schedulerdb. You can place a vote for it to make it happen.

Actually, even on the top AMQ HA solution, LevelDB+ZooKeeper, the scheduler is taken out of the game and documented to create issues ( http://activemq.apache.org/replicated-leveldb-store.html at end of page).

In a JDBC scenario, therefor it can be considered unsafe and unsupported, but at least not clearly documented, how to setup the datastore for the redelivery policy.